Concrete blocks for free standing and retaining walls have been known and used for many years. They can be both functional and decorative, and range from small gardening applications to large-scale construction projects. Such walls are typically used to form horizontal surfaces or terraces by providing a generally vertically extending barrier behind which backfill may be deposited. Such walls reduce erosion and slumping, maximize land use, and can provide an attractive and decorative appearance.
Retaining walls can be constructed from stackable concrete blocks. Blocks are stacked in horizontal rows called courses. Multiple successive courses may be used to create a vertically rising wall of a desired height. Often, there will be a slight setback between adjacent courses so that the wall gradually slopes backwards as it gets taller, which helps the wall resist loads from the earth retained behind it. These types of blocks can generally be assembled quickly and economically due to the interlocking of adjacent courses of blocks. A type of retaining wall that can be built using blocks known as mechanically stabilized earth retaining walls employs either metallic or polymeric tensile reinforcements, often referred to as grids, in the earth mass behind the wall. The grids extend horizontally from between adjacent courses of blocks back into the soil, which creates a stronger wall more resistant to tipping.
Concrete wall blocks are typically manufactured using the conventional dry cast manufacturing process. In such process, a zero slump concrete mixture is introduced into a mold apparatus. Then a head compresses the mixture in the mold to form a slug that is subsequently cured and often split into two wall blocks.
Retaining walls for large-scale applications can require rather large blocks. Blocks weighing between 60 and 100 pounds or larger are commonly used. Such blocks increase the strength of the wall due to their weight and depth. These characteristics give them enhanced ability to hold grids in place. However, large blocks make building a wall a much more arduous task due to their size and weight. This tends to increase the labor costs associated with building a wall out of such blocks.
Larger blocks are also more expensive to make and ship. Fewer blocks can be made at one time in a mold, so production is slower and more concrete mix must be used. Also, due to weight and height restrictions on the trucks that transport the blocks, fewer larger blocks can be shipped at a time so transportation costs are increased.